Fracturing liquid

ABSTRACT

A subterranean fracturing fluid, which is relatively harmless to both the environment and subterranean formations includes an amphoteric surfactant, specifically a betaine surfactant and an organic electrolyte or an alcohol in an aqueous medium. Depending upon the proportions of the ingredients, the fluid can be foamed.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a fracturing fluid and to a method offracturing a subterranean formation to increase the permeability of theformation.

[0003] More specifically, the invention provides a foamed, viscoelasticsurfactant based fracturing fluid for fracturing a subterraneanformation and transporting proppant into thus created fractures.

[0004] 2. Discussion of the Prior Art

[0005] Hydraulic fracturing has been used for many years to stimulatethe production of petroleum from subterranean formations. In hydraulicfracturing, a fracturing fluid is injected through a wellbore into theformation at a pressure and flow rate sufficient to overcome theoverburden stress and to initiate a fracture in the formation.Frequently, a proppant, whose function is to prevent the createdfractures from closing back down upon itself when the pressure isreleased, is suspended in the fracturing fluid for transport into afracture. Proppants in use include, for example 20-40 mesh size sand andceramics, but the most common proppant is sand. The proppant filledfractures provide permeable channels allowing petroleum to seep throughthe fractures into the wellbore from whence it is pumped to the surface.Accordingly, a desired fracturing fluid should have the followingproperties: (a) compatibility with the reservoir rock and reservoirfluids, (b) be sufficiently viscous and have a fluid structure capableof suspending proppants and transport them deep into the formation, (c)be stable enough to retain sufficient viscosity and fluid structurethroughout proppant placement, (d) possess low fluid loss properties andlow fluid flow friction pressures, (e) be easily removed from theformation with little residue, (f) be easily made under field conditionsand (g) be relatively inexpensive. Production of petroleum can beenhanced significantly by the use of specialized fracturing fluids,which exhibit high levels of rheological performance.

[0006] Fracturing fluids in common use include various aqueous gels andhydrocarbon gels. The gels are formed by introducing cross-linkablepolymers or surfactants into an aqueous or hydrocarbon fluid, followedby cross-linking of the polymer or surfactant molecules. Thecross-linking give the fluid high viscoelastic properties that arenecessary to transport and place proppants into the fractures.

[0007] Another widely used fracturing fluid is foramed, water-basedfracturing fluid. Such a fluid is described, for example, in U.S. Pat.No. 3,980,136, issued to R. A. Plummer et al on Sep. 14, 1976. Briefly,the foamed fracturing process involves generation of foams with adesired quality which are pumped through a wellbore into a formation.Typically, for aqueous systems, a polymer has to be hydrated in water atthe surface before being pumped into the formation. The process ofpolymer hydration is time consuming and often requires bulky equipmentat the wellsite. Another problem common to polymer-based fracturingfluids is that a significant amount of polymer residue is left in theformation resulting in negative impact on formation permeability.

[0008] Viscoelastic surfactants have long been used for wellstimulation. A surfactant is a type of substance, which contains bothhydrophobic and hydrophilic groups in the same molecule. The hydrophobicgroup is usually one of a variety of alkyl groups and the hydrophilicgroup can be ionic, which may be positive (cationic), negative (anionic)or contain both positive and negative moieties (amphoteric), ornonionic—often consisting of a neutral polyoxyalkylene group. Whendissolved in an aqueous medium, surfactants generally form variousaggregates called micelles above a critical micelle concentration (cmc).At low concentration of surfactant, the micelles usually are small andspherical. Under certain conditions and surfactant concentrations,however, the spherical micelles grow in size and/or change their shaperesulting in the formation of long flexible micelles. Above a certainconcentration the long flexible micelles can become entangled andexhibit strong visoelastic behavior. Even though this feature has beenobserved in a number of systems containing nonionic and anionicsurfactants, the effect is more pronounced in cationic surfactants,especially those containing an amine or quaternary ammonium group, inthe presence of certain organic counterions such as, for examplesalicylate, benzonate and alkyl sulfonate. Viscoelastic surfactantfluids have been studied extensively in recent years and have found awide variety of uses in many applications.

[0009] U.S. Pat. No. 4,061,580, issued to R. W. Jahnke on Dec. 6, 1977discloses surfactant gelled fracturing and acidizing fluids suitable forwell stimulation. The gelled fluids are prepared by adding certain aminesalts to aqueous acid or salt solutions. The amine salts used asthickeners are prepared by merely mixing one equivalent of amine perequivalent of acid or, in the case of polybasic acids such as sulfuricand phosphoric acids, as little as one-half equivalent of amine perequivalent of acid may be used resulting in the formation of an acidicsalt. The aqueous acid or salt solution can be gelled by the addition ofthe above-described salts. For example, 15% by weight of HCl can begelled by the addition of a small amount, usual 3-10% by weight andtypically about 5% by weight of an amine or amine salt as describedabove. For fracturing fluids, aqueous solutions containing someinorganic salts can be gelled by the addition of 3-10% by weight,preferably about 5% by weight, of an amine salt described above.

[0010] U.S. Pat. No. 4,163,727, issued to C. G. Inks on Aug. 7, 1979discloses an acidizing-gel composition which consists essentially of,for example, about 15% by weight of HCl, about 20% by weight of asuitable nonionic gel-forming surfactant containing oxyethylene andoxypropylene units, a corrosion inhibitor to the extent needed, and thebalance water.

[0011] U.S. Pat. Nos. 5,551,516, issued to W. D. Norman et al on Sep. 3,1996 and 5,964,295, issued to J. E. Brown et al on Oct. 12, 1999disclose a fracturing fluid composition comprising a quaternary ammoniumsalt, erucyl bis (2-hydroxyethyl) methyl ammonium chloride, an organicsalt such as sodium salicylate, inorganic salts such as ammoniumchloride and potassium chloride and water. The patents state that thefluid has good viscoelastic properties and is easily formulated andhandled. Furthermore, no or very little residue is left in a formationafter the completion of the fracturing process. It is worth noting,however, that cationic surfactants such as amine and quaternary ammoniumsalts usually degrade very slowly, both aerobically and anaerobically,and moreover are highly toxic to marine organisms. The combination oflow biodegradability and high toxicity is a fundamental criterion for aproduct injurious to the environment. In addition, cationic surfactantstend to rend the formation, especially sandstone formations, oil-wetadsorbing on the surface of clays and sands. The alteration of theformation wettability often reduces the relative permeability ofpetroleum leading to high water/petroleum ratio and low productionrates. The strong adsorption of cationic surfactant on the clay andsands may also adversely affect fluid viscosity.

GENERAL DESCRIPTION OF THE INVENTION

[0012] Thus, there is a general demand for surfactants, which are lessharmful to both the environment and to subterranean formations, butwhich have the same excellent ability as above-mentioned cationicsurfactants to form viscoelastic surfactant based fracturing fluids. Anobject of the present invention to meet this demand.

[0013] Another object of the present invention is to overcome thedisadvantages inherent to existing fracturing fluids by providing afracturing fluid having relatively good foaming capability and foamstability in a wide range of temperatures.

[0014] According to one aspect, the invention relates to a fracturingfluid comprising an aqueous medium, at least one betaine surfactanthaving a saturated or unsaturated alkyl or acyl group containing 14-24carbon atoms and a member selected from the group consisting of (a) atleast one organic electrolyte having the general formula

R₁-A

[0015] wherein R₁ is a hydrophobic aliphatic or aromatic, straight orbranched, saturated or unsaturated hydrocarbon group with 6-24 carbonatoms and A is a cationic, preferably monovalent group and (b) at leastone alcohol having the general formula

R₂—OH

[0016] wherein R₂ is a hydrocarbon group with 6-24 carbon atoms.

[0017] According to a second aspect, the invention relates to a methodof fracturing a subterranean formation comprising the step of injectinga fracturing fluid into the formation at a pressure sufficient toinitiate fracturing, said fluid including an aqueous medium, at leastone betaine surfactant having a saturated or unsaturated alkyl or acylgroup containing 14-24 carbon atoms and a member selected from the groupconsisting of (a) at least one organic electrolyte having the generalformula

R₁-A

[0018] wherein R₁ is a hydrophobic aliphatic or aromatic, straight orbranched, saturated or unsaturated hydrocarbon group with 6-24 carbonatoms and may also contain one or two hydrophilic moieties, and A is acationic preferably monovalent group, and (b) at least one alcoholhaving the general formula

R₂—OH

[0019] wherein R₂ is a hydrocarbon with 6-24 carbon atoms.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0020] As described above, the basic composition of the inventionincludes surfactant, and the organic electrolyte or alcohol which areall readily degradable. In addition, since betaine surfactants havestrong foaming capability, the present composition also gives anexcellent foaming capability and foam stability within wide temperatureranges, without employing additional foaming surfactants. The presentfluid may also contain a gas, for example, N₂ or CO₂, and thereby be inthe form of foams or energized fluids. In other words, the present fluidmay also be utilized as a foamed water-based fracturing fluid in thepresence of gas.

[0021] The betaine surfactant has a saturated or unsaturated alkyl oracyl group with 14-24 carbon atoms. When the surfactant is used with theorganic electrolyte of the formula R₁-A, the generally molecularstructure of the betaine surfactants is represented by the generalformula

[0022] where R₃ is an alkyl group or the group R′NHC₃H₆, in which R′ isan acyl group. The groups R₃ and R′ can suitably be tetradecyl,hexadecyl, octadecyl, oleyl, rape seed alkyl and tallow alkyl or thecorresponding acyl group.

[0023] As mentioned above the organic electrolyte has the generalformula

R₁-A

[0024] where R₁ is a hydrocarbon group with 6-24 carbon atoms and A is acationic, preferably monovalent group. The hydrophobic group R₁ can bealiphatic or aromatic, straight or branched, saturated or unsaturatedand may also contain one or two hydrophilic moieties The combination ofthe specific betaine surfactants and the organic electrolytes in anaqueous medium gives good viscoclastic properties within a widetemperature range. The fluids according to the invention can alsotolerate hard water and a high concentration of salt. The carbon numbersof the hydrophobic groups, R₃ R′ and R₁ will determine the usefultemperature range for a particular fluid so that high carbon numbersusually give products suitable for high temperatures.

[0025] When the betaine surfactant is used with an alcohol of theformula R₂—OH the general formula of the betaine surfactant is

[0026] where R₃ has the above-defined meaning, and R₄ and R₅ arehydrocarbon aliphatic or unsaturated groups and may also containn one ortwo hydrophilic moieties, such as hydroxyl(—OH), or ethoxy or propoxymoieties. In the alcohol having the general structure

R₂—OH

[0027] R₂ is a hydrocarbon group with 6-24 carbon atoms. The hydrocarbongroups R₂ can be aliphatic or aromatic, straight or branched, saturatedor unsaturated. The combination of the specific betaine surfactants andalcohols in an aqueous medium also gives good viscoelastic propertieswithin a given temperature range. The carbon numbers of the hydrocarbongroups R₃ will determine the useful temperature range for a particularfluid so that high carbon numbers usually give products suitable forhigh temperatures.

[0028] When the surfactant is used in combination with an organicelectrolyte, the preferred betaine surfactant is hexadecyl dimethylbetaine or octadecyl dimethyl betaine. Alternative betaines may beemployed either alone or in combination, including rapeseed alkyldimethyl betaine, oleyl, dimethyl betaine, tallow dimethyl betaine,myristyl dimethyl betaine. The preferred organic electrolyte is sodiumsalt of 3-hydroxy-2-Naphthalene carboxylic acrd. Alternatives includesodium xylene sulphonate, sodium 3-hydroxy-2-sodium cumene sulphonate,sodium salicylate, sodium dodecyl benzene sulphonate, sodium toluenesulphonate, sodium toluate, sodium benzene sulphonate, sodium,hexadecylbenzenesulphonate, sodium phenyl phosphate, alkyl sulphatesderived from fatty alcohols or synthetic alcohols, andalkylarenesulphonates such as decylsulphate, dodecylsulphate,cocoalkylsulphate, oleylsulphate, tallowsulphate. It is worth notingthat it is the anions instead of the cations, of the organic electrolytewhich promote the formation of the viseoelastic surfactant gel whenmixed with the betaine surfactants in the aqueous medium.

[0029] When the surfactant is used with an alcohol, the preferredbetaine surfactant is octadecyl dimethyl betaine. Alternative betainesmay be employed either alone or in combination, including erucyldimethyl betaine, docosyl dimethyl betaine, cetyl, dimethyl betaine,tallow dimethyl betaine, and myristyl dimethyl betaine. The preferredalcohol is benzyl alcohol. Alternatives include decanol, dodecanol andhexadecanol.

[0030] By “aqueous medium” is meant that at least 50% by weight,preferably at least 90% by weight, of the water-based liquid systemconsists of water. Within the term are plain water and aqueous solutionsof inorganic salts and aqueous alkaline or acidic solution. Otherexemplary aqueous liquids include mixtures of water and water-miscibleliquids such as lower alkanols, e.g., methanol, ethanol or propanol,glycols and polyglycols. Also included are emulsions of immiscibleliquids in the aqueous liquids, aqueous slurries of solid particulatessuch as sands, ceramics, or other minerals and a number of conventionalcomponents such as clay stabilizers, antifreeze agents and bactericides.All of the additives, as well as the betaine surfactants, organicelectrolytes and water, are employed in amounts that do notdeleteriously affect the viscoelastic properties of the fluid.

[0031] The present invention is described below in greater detail bymeans of the following examples.

EXAMPLES

[0032] The foaming properties of the surfactant and organic electrolytecompositions according to the present invention were tested by a simplemethod involving the measuring of foam height and foam half-life.

[0033] 200 ml of gel sample were placed in a 1 litre Waring blender jar,and mixed at maximum blender speed for 30 seconds. The resulting foamwas poured into a 1000 ml graduated cylinder, and a timer started. Thefoam height is the maximum volume occupied by the foam, and can be usedto calculate foam quality. The half-life is the time required for 100 mlof solution to accumulate in the bottom of the cylinder. For elevatedtemperatures, the sample, blender jar, and cylinder are heated to 10 C.above the tested temperature for 15 minutes. In the following examples,the percentages are by weight and the viscosity is measured using aBrookfield viscometer (Model LVT, Spindle 1 at 12 rpm) at roomtemperature.

Example 1

[0034] 0.50 g of N-hexadecyl dimethyl betaine having the formula

CH₃(CH₂)₁₅N⁺(CH₃)₂CH₂COO—

[0035] (hereinafter referred to as C₁₆-betaine or C₁₆-BET) was dissolvedin 0.4 ml isopropanol (IPA) and then mixed with 200 ml of tap water. Theresulting solution was mixed with 0.27 g of the sodium salt of dodecylbenzene sulphonate having the formula

CH₁₂H₂₅C₆H₄SO³⁻Na⁺

[0036] (hereinafter referred to as Na-LAS). A clear gel with highelasticity was formed. The gel was poured into a 1 litre Waring blenderjar, and mixed at maximum blender speed for 30 seconds. The resultingfoam was tested in the manner described above. The test results arelisted in Table

Example 2

[0037] 0.50 g of C₁₆-BET was dissolved in 0.4 ml IPA, and then mixedwith 200 ml of 7.0 wt % of aqueous KCI solution. The resulting solutionwas mixed with 0.098 g of the sodium salt of3-hydroxy-2-naphthalenecarboxylic acid, C₁₀H₆(OH)COONa, (in thefollowing called Na-BON). A clear gel with high elasticity was formed.The gel was tested in the same manner as in Example 1. The results areshown in Table I.

Example 3

[0038] 0.60 g of C₁₈-betaine (C₁₈-BET) was first dissolved in 1 mlisopropanol and then mixed with 200 ml of 7.0 wt % of aqueous KCIsolution. The resulting solution was mixed with 0.098 g of Na-BON. Aclear gel with high elasticity was formed. The gel was tested in thesame manner as in Example 1. The results are shown in Table I.

Example 4

[0039] 0.50 g C₁₈-BET was dissolved in 200 ml of 7. wt % of aqueous KCIsolution at 40 C. and then mixed with 0.7 g of sodium xylene sulfonate(in the following called Na-XS). A clear gel with high elasticity wasformed. The gel was cooled to room temperature. The gel was tested inthe same manner as in Example 1. The results are shown in Table I.

Example 5

[0040] 200 ml of gel with the composition specified in Example 4 wasfirst subjected to saturation of CO₂ and then tested in the same manneras in Example 1. No significant changes in viscosity and foam propertieswere observed.

Example 6

[0041] 200 ml of gel with the composition specified in Example 4 wasfirst subjected to saturation of N₂ and then tested in the same manneras in Example 1. No significant changes in viscosity and foam propertieswere observed. TABLE 1 Composition (approximategel (cp) Viscosity ofbase Foam height % by weight) (ml) (min) Foam Half-Life (1) 35 600 220.25 C₁₆-BET 0.075 Na-LAS 0.2 IPA balance water (2) 250 400 70 0.25C₁₆-BET 0.049 Na-BON 0.2 IPA 7 KCl balance of water (3) 350 300 7 0.30C₁₈-BET 0.049 Na-BON 0.5 IPA 7 KCl balance of water (4) 285 620 45 0.40C₁₈-BET 0.25 Na-XS 7 KCl balance of water

[0042] From the results for the above examples, it is evident thatC₁₆-betaine and C₁₈-betaine in combination with an organic saltelectrolyte has good foaming capability and can be used for foamfracturing applications.

Example 7

[0043] 1.0 g of C₁₈-BET was dissolved in 0.4 ml of IPA, and then mixedwith 200 ml of 7.0% wt % of aqueous KCL solution. The resulting solutionwas mixed with 0.17 g of Na-LAS. A clear gel with high elasticity wasformed. The viscosity of the gel was tested in the manner describedabove, and the results are listed in Table 2.

Example 8

[0044] 0.75 g of C₁₆-BET was dissolved in 0.4 ml of IPA, and then mixedwith 200 ml of 7.0 wt % of aqueous KCI solution. The resulting solutionwas mixed with 0.27 of Na-BON in NaOH solution. A clear gel with highelasticity was formed. The gel was tested in the same manner as inExample 7. The results are shown in Table 2.

Example 9

[0045] 0.50 g of C₁₈-BET was first dissolved in 0.5 ml IPA and thenmixed with 200 ml of 7.0 wt % of aqueous KCI solution at 40 C. Theresulting solution was mixed with 0.14 g of Na-BON in NaOH solution. Aclear gel with high elasticity was formed. The gel was cooled to roomtemperature and tested in the same manner as in Example 7. The resultsare shown in Table 2.

Example 10

[0046] 1.0 g of C₁₈-BET was premixed with 0.8 ml of ethylene glycolmonobutyl ether (EGMBE), 0.6 g of Na-XS and 0.4 ml of hot water. Theresulting mixture was than mixed with 200 ml of 7.0 wt % of aqueous KCIsolution at room temperature. A clear elastic gel was formedimmediately. The gel was tested in the same manner as in Example 7. Theresults are shown in Table 2.

Example 11

[0047] 0.75 g of C₁₈-BET was premixed with 0.8 ml of EGMBE, 0.6 g ofNa-XS and 0.4 ml of hot water. The resulting mixture was then mixed with200 ml of 7.0 wt % of aqueous KCI solution at room temperature. A clearelastic gel was formed immediately. The gel was tested in the samemanner as in Example 7. The results are shown in Table 2. TABLE 2Compositions Viscosity of gels (approximate % by weight) (cp) (7) 2400.5 C₁₈-BET 0.85 Na-LAS 0.20 IPA 7.0 KCl balance of water (8) 1050 0.38C₁₆-BET 0.14 Na-BON 0.2 IPA 7.00 KCl balance of water (9) 300 0.25C₁₈-BET 0.070 Na-BON 0.50 IPA 7.00 KCl balance of water (10) 855 0.50C₁₈-BET 0.30 Na-XS 0.40 EGMBE 7.00 KCl balance of water (11) 570 0.38C₁₈-BET 0.30 Na-XS 0.40 EGMBE 7.00 KCl balance of water

Example 12

[0048] 200 ml of gel with the composition specified in Table 2 forExample 10 was first subjected to saturation with CO₂ and then tested inthe manner described above. No significant changes in viscosity and foamproperties were observed.

Example 13

[0049] 200 ml of gel with the composition specified in Table 2 forExample 10 was first subjected to saturation with N₂ and then tested inthe manner described above. No significant changes in viscosity and foamproperties were observed.

[0050] From the results of testing set out in Table 2 it is evident thatcombinations of a betaine surfactant and an organic electrolyte in theaqueous medium form clear gels with good viscoelastic properties. Thesegels can be used for hydraulic fracturing applications. For applicationsrequiring higher viscosity, higher surfactant loading is generallyrequired.

[0051] The foaming properties of the surfactant and organic alcoholcompsoitions according to the present invention were tested by a simplemethod involving the measuring the viscosity of the gel.

Example 14

[0052] 1.5 g active substance of octadecyl dimethyl betaine (in thefollowing called C₁₈-betaine) was first dissolved in 200 ml of 5 wt %KCl aqueous solution. The resulting surfactant solution was mixed with0.8 g of hexadecanol at 55° C. A clear gel with high elasticity wasformed. the viscosity of the gel was measured using a Brookfieldviscometer (Model LVT, Spindle 1 at 12 rpm) at 55° C. The results arelisted in Table 3.

Example 15

[0053] 1.5 g of C18-betaine was first dissolved in 200 ml of 5 wt % KClaqueous solution. The resulting surfactant solution was mixed with 0.6 gof tetradecanol at 40° C. A clear gel with high elasticity was formed.The viscosity of the gel was measured suing a Brookfield viscometer(Model LVT, Spindle 1 at 12 rpm) at 40° C. The results are listed inTable 3.

Example 16

[0054] 1.5 g of C18-betaine was first dissolved in 200 ml of 5 wt % KClaqueous solution. The resulting surfactant solution was mixed with 0.2 gof decanol at 30° C. A clear gel with high elasticity was formed. Theviscosity of the gel was measured using a Brookfield viscometer (ModelLVT, Spindle 1 at 12 rpm) at 30° C. The results are shown in Table 3.

Example 17

[0055] 1.0 g of C18-betaine was first dissolved in 200 ml of 5 wt % KClaqueous solution. The resulting surfactant solution was mixed with 0.5 gof benzyl alcohol at 22° C. A clear gel with high elasticity was formed.The viscosity of the gel was measured using a Brookfield viscometer(Model LVT, Spindle 1 at 12 rpm) at 22° C. The results are shown inTable 3.

Example 18

[0056] 1.5 of C16-betaine was first dissolved in 200 ml of 5 wt % KClaqueous solution. The resulting surfactant solution was mixed with 0.6 gof benzyl alcohol at 22° C. A clear gel with high elasticity was formed.The viscosity of the gel was measured using a Brookfield viscometer(Model LVT, Speindle 1 at 12 rpm) at 22° C. The results are shown inTable 3. TABLE 3 Compositions Viscosity of gels 1. C18-Betaine 0.78% 340cp Hexadecanol 0.4% KCl 5.0% 2. C18-Betaine 0.75% 470 cp Tetradecanol0.3% KCl 5.0% 3. C18-Betaine 0.75% 750 cp Decanol 0.1% KCl 5.0% 4.C18-Betaine 0.5% 660 cp Benzyl alcohol 0.25% KCl 5.0% 5. C16-Betaine0.75% 220 cp Benzyl alcohol 0.3% KCl 5.0%

[0057] From the results of testing set out in Table 3 it is evident thatcombinations of a betaine surfactant and an organic electrolyte in theaqueous medium form clear gels with good viscoelastic properties. Thesegels can be used for hydraulic fracturing applications. For applicationsrequiring higher viscosity, higher surfactant loading is generallyrequired. The present fluid may also contain a gas, for example N₂ orCO₂, and thereby be in the form of foams or energized fluids. In otherwords, the present fluid may also be utilized as a foamed water-basedfracturing fluid in the presence of gas.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A fracturing fluidcomprising an aqueous medium, at least one betaine surfactant having asaturated or unsaturated alkyl or acyl group containing 14-24 carbonatoms and a member selected from the group consisting of (a) at leastone organic electrolyte having the general formula R₁-A wherein R₁ is ahydrophobic aliphatic or aromatic, straight or branched, saturated orunsaturated hydrocarbon group with 6-24 carbon atoms and A is a cationicmonovalent group, and (b) at least one alcohol having the generalformula R₂—OH wherein R₂ is a hydrocarbon group with 6-24 carbon atoms.2. The fracturing fluid of claim 1, wherein the group R₁ contains 1-2hydrophilic groups selected from hydroxyl, ethoxy and propoxy.
 3. Thefracturing fluid of claim 1, including the betaine and the organicelectrolyte, the surfactant having the general formula

wherein R₃ is an alkyl group or the group R′NC₃H₆—, wherein R′ is analkyl group.
 4. The fracturing fluid of claim 1, wherein said organicelectrolyte is selected from the group consisting of sodium3-hydroxy-2-naphthalenecarboxylate; sodium xylene sulphonate; sodiumcumene sulphonate; sodium salicylate, sodium dodecyl benzene sulphonate,sodium toluene sulphonate, sodium toluate, sodium benzene sulphonate,sodium; hexadecylbensensulphonate, sodium phenyl phosphate, alkylsulphates derived from fatty alcohols or synthetic alcohols, andalkylarenesulphonates.
 5. The fracturing fluid of claim 4, wherein saidorganic electrolyte is selected from the group consisting of sodiumsalts of decylsulphate, dodecylsulphate, cocoalkylsulphate,oleylsulphate, tallowsulphate and mixtures thereof.
 6. The fracturingfluid of claim 1, wherein said aqueous medium is selected from the groupconsisting of water, an aqueous solution of an inorganic salt, aqueousalkaline or acid solution, water and a lower alkanol, glycol orpolyglycol and mixtures thereof.
 7. The fracturing fluid of claim 3,wherein said alkyl group of the-betaine surfactant contains 14-22 carbonatoms.
 8. The fracturing fluid of claim 3, wherein said alkyl group ofthe betaine surfactant contains 14-22 carbon atoms and 1-2 double bonds.9. The fracturing fluid of claim 3, wherein the acyl group of thebetaine surfactant contains 14-22 carbon atoms.
 10. The fracturing fluidof claim 3, wherein the acyl group of said betaine surfactant contains14-22 carbon atoms and 1-2 double bonds.
 11. The fracturing fluid ofclaim 4, wherein the acyl group of said betaine surfactant contains14-22 carbon atoms and 1-2 double bonds.
 12. The fracturing fluid ofclaim 1, wherein said aqueous medium is a mixture of water andisopropanol, said betaine surfactant is hexadecyl dimethyl betaine andsaid organic electrolyte is the sodium salt of dodecyl benzenesulphonate.
 13. The fracturing fluid of claim 1, wherein said aqueousmedium is a solution of KCl in water and isopropanol, said betainesurfactant is hexadecyl dimethyl betaine and said organic electrolyte isthe sodium salt of 3-hydroxy-2-naphthalene carboxylic acid.
 14. Thefracturing fluid of claim 1, wherein said aqueous medium is a solutionof KCl in water and isopropanol, said betaine surfactant is octadecyldimethyl betaine and said organic electrolyte is the sodium salt of3-hydroxy-2-naphthalenecarboxylic acid.
 15. The fracturing fluid ofclaim 1, wherein said aqueous medium is a solution of KCl in water andisopropanol, said betaine surfactant is octadecyl dimethyl betaine andsaid organic electrolyte is sodium xylene sulphonate.
 16. The fracturingfluid of claim 1, wherein said aqueous medium is water and isopropanol,said betaine surfactant is octadecyl dimethyl betaine and said organicelectrolyte is the sodium salt of dodecyl benzene sulphonate.
 17. Thefracturing fluid of claim 1, wherein said aqueous medium is a solutionof KCl in water and isopropanol, said betaine surfactant is hexadecyldimethyl betaine and said organic electrolyte is the sodium salt ofdodecyl benzene sulphonate.
 18. The fracturing fluid of claim 1, whereinsaid aqueous medium is a solution of KCl in water and ethylene glycolmonobutyl ether, said betaine surfactant is octadecyl dimethyl betaineand said organic electrolyte is sodim xylene sulphonate.
 19. Thefracturing fluid of claim 1, wherein the surfactant is used with thealcohol, and the betaine surfactant has the general formula

wherein R₃ is an alkyl group or the group R′NC₃H₆—, wherein R′ is analkyl group, and R₄ and R₅ are hydrocarbon aliphatic or aromatic,straight or branched, saturated or unsaturated groups.
 20. Thefracturing fluid of claim 19, wherein the groups R₁ and R₂ contain 1-2hydrophilic moieties selected from hydroxyl, ethoxy or propoxy.
 21. Thefracturing fluid of claim 19, wherein said alcohol is selected from thegroup consisting of benzyl alcohol, decanol, dodecanol or hexadecanol.22. The fracturing fluid of claim 19, wherein said aqueous medium isselected from the group consisting of water, an aqueous solution of aninorganic salt, aqueous alkaline or acid solution, water and a loweralkanol, glycol or polyglycol and mixtures thereof.
 23. The fracturingfluid of claim 19, wherein said betaine surfactant is selected from thegroup consisting of erucyl dimethyl betaine, docosyl dimethyl betaine,octadecyl dimethyl betaine cetyl dimethyl betaine, and tallow dimenthylbetaine and myristyl dimethyl betaine.
 24. The fracturing fluid of claim19, wherein said aqueous medium is a solution of KCl in water, saidbetaine surfactant is octadecyl dimethyl betaine and said alcohol ishexadecanol.
 25. The fracturing fluid of claim 19, wherein said aqueousmedium is a solution of KCl in water, said betaine surfactant isoctadecyl dimethyl betaine and said alcohol is tetradecanol.
 26. Thefracturing fluid of claim 19, wherein said aqueous medium is a solutionof KCl in water, said betaine surfactant is octadecyl dimethyl betaineand said alcohol is decanol.
 27. The fracturing fluid of claim 19,wherein said aqueous medium is a solution of KCl in water, said betainesurfactant is octadecyl dimethyl betaine and said alcohol is benzylalcohol.
 28. The fracturing fluid of claim 19, wherein said aqueousmedium is a solution of KCl in water, said betaine surfactant ishexadecyl dimethyl betaine and said alcohol is benzyl alcohol.
 29. Amethod of fracturing a subterranean formation comprising the step ofinjecting a fracturing fluid into the formation oat a pressuresufficient to initiate fracturing, said fluid including an aqueousmedium, at least one betaine surfactant having a saturated orunsaturated alkyl or acyl group containing 14-24 carbon atoms and amember selected from the group consisting of (a) at least one organicelectrolyte having the general formula R₁-A wherein R₁ is a hydrophobicaliphatic or aromatic, straight or branched, saturated or unsaturatedhydrocarbon group with 6-24 carbon atoms and may also contain one or twohydrophilic moieties, and A is a cationic preferably monovalent group,and (b) at least one alcohol having the general formula R₂—OH wherein R₂is a hydrocarbon with 6-24 carbon atoms.
 30. The method of claim 29,wherein the group R₁ contains 1-2 hydrophilic groups selected fromhydroxyl, ethoxy and propoxy.
 31. The method of claim 29, including thebetaine and the organic electrolyte, the surfactant having the generalformula

wherein R₃ is an alkyl group or the group R′NC₃H₆, wherein R′ is analkyl group.
 32. The method of claim 29, wherein said organicelectrolyte is selected form the group consisting of sodium xylenesulphonate; sodium cumene sulphonate; sodium salicylate, sodium dodecylbenzene sulphonate, sodium toluene sulphonate, sodium toluate, sodiumbenzene sulphonate, sodium; hexadecylbensensulphonate, sodium phenylphosphate, alkyl sulphates derived from fatty alcohols or syntheticalcohols, and alkylarenesulphonates.
 33. The method of claim 32, whereinsaid organic electrolyte is selected from the group consisting of sodiumsalts of decylsulphate, dodecylsulphate, cocoalkylsulphate,oleylsulphate, tallowsulphate and mixtures thereof.
 34. The method ofclaim 29, wherein said aqueous medium is selected from the groupconsisting of water, an aqueous solution of an inorganic salt, aqueousalkaline or acid solution, water and a lower alkanol, glycol orpolyglycol and mixtures thereof.
 35. The method of claim 31, whereinsaid alkyl group of the betaine surfactant contains 14-22 carbon atoms.36. The method of claim 31, wherein said alkyl group of the betainesurfactant contains 14-22 carbon atoms and 1-2 double bonds.
 37. Themethod of claim 31, wherein the acyl group of the betaine surfactantcontains 14-22 carbon atoms.
 38. The method of claim 31, wherein theacyl group of said betaine surfactant contains 14-22 carbon atoms and1-2 double bonds.
 39. The method of claim 32, wherein said betainesurfactant is selected from the group cnsisting of hexadecyl dimethylbetaine and octadecyl dimethyl betaine.
 40. The method of claim 29,wherein said aqueous medium is a mixture of water and isopropanol, saidbetaine surfactant is hexadecyl dimethyl betaine and said organicelectrolyte is the sodium salt of dodecyl benzene sulphonate.
 41. Themethod of claim 29, wherein said aqueous medium is a solution of KCl inwater and isopropanol, said betaine surfactant is hexadecyl dimethylbetaine and said organic electrolyte is the sodium salt of3-hydroxy-2-naphthalene carboxylic acid.
 42. The method of claim 29,wherein said aqueous medium is a solution of KCl in water andisopropanol, said betaine surfactant is octadecyl dimethyl betaine andsaid organic electrolyte is the sodium salt of3-hydroxy-2-naphthalenecarboxylic acid.
 43. The method of claim 29,wherein said aqueous medium is a solution of KCl in water andisopropanol, said betaine surfactant is octadecyl dimethyl betaine andsaid organic electrolyte is sodium xylene sulphonate.
 44. The method ofclaim 29, wherein said aqueous medium is water and isopropanol, saidbetaine surfactant is octadecyl dimethyl betaine and said organicelectrolyte is the sodium salt of dodecyl benzene sulphonate.
 45. Themethod of claim 29, wherein said aqueous medium is a solution of KCl inwater and isopropanol, said betaine surfactant is hexadecyl dimethylbetaine and said organic electrolyte is the sodium salt of dodecylbenzene sulphonate.
 46. The method of claim 29, wherein said aqueousmedium is a solution of KCl in water and ethylene glycol monobutylether, said betaine surfactant is octadecyl dimethyl betaine and saidorganic electrolyte is sodim xylene sulphonate.
 47. The method of claim29, wherein the surfactant is used with the alcohol, and the betainesurfactant has the general formula

wherein R₃ is an alkyl group or the group R′NC₃H₆—, wherein R′ is analkyl group, and R₄ and R₅ are hydrocarbon aliphatic or aromatic,straight or branched, saturated or unsaturated groups.
 48. The method ofclaim 47, wherein the groups R₁ and R₂ contain 1-2 hydrophilic moietiesselected from hydroxyl, ethoxy or propoxy.
 49. The method of claim 47,wherein said alcohol is selected from the group consisting of benzylalcohol, decanol, dodecanol or hexadecanol.
 50. The method of claim 47,wherein said aqueous medium is selected from the group consisting ofwater, an aqueous solution of an inorganic salt, aqueous alkaline oracid solution, water and a lower alkanol, glycol or polyglycol andmixtures thereof.
 51. The method of claim 47, wherein wherein saidbetaine surfactant is selected from the group consisting of erucyldimethyl betaine, docosyl dimethyl betaine, octadecyl dimethyl betainecetyl dimethyl betaine, and tallow dimenthyl betaine and myristyldimethyl betaine.
 52. The method of claim 47, wherein said aqueousmedium is a solution of KCl in water, said betaine surfactant isoctadecyl dimethyl betaine and said alcohol is hexadecanol.
 53. Themethod of claim 47, wherein said aqueous medium is a solution of KCl inwater, said betaine surfactant is octadecyl dimethyl betaine and saidalcohol is tetradecanol.
 54. The method of claim 47, wherein saidaqueous medium is a solution of KCl in water, said betaine surfactant isoctadecyl dimethyl betaine and said alcohol is decanol.
 55. The methodof claim 47, wherein said aqueous medium is a solution of KCl in water,said betaine surfactant is octadecyl dimethyl betaine and said alcoholis benzyl alcohol.
 56. The method of claim 47, wherein said aqueousmedium is a solution of KCl in water, said betaine surfactant ishexadecyl dimethyl betaine and said alcohol is benzyl alcohol.